The present invention relates to a sheet discharge device for carrying out treatments such as accumulating a plurality of sheets discharged from an image forming apparatus such as a copying device or a printer to match them, and stapling (staple) a bundle of sheets thus matched, and an image forming apparatus provided with such a sheet discharge device as described.
The image forming apparatus receives image data to be printed from a data treatment device, for example, such as an image reading device, a facsimile device, or a computer, to form a printed image on the sheet on the basis thereof.
The sheet discharge device receives a sheet after image formation from the image forming apparatus to discharge it onto a sheet discharge tray. However, in case where a plurality of sheets after image formation is present, ends of a bundle of sheets are matched; or the ends of a bundle of sheets are subjected to stapling as necessary; and as the case may be, discharge such as boring a punch hole is carried out. The bundle of sheets applied with such a discharge as described is finally stacked sequentially on the accumulation tray, and taken out by an operator.
In the sheet discharge device as described above, corresponding to the fact that the image forming apparatus is able to handle sheets of various kinds of sizes, it is necessary to carry out post-treatment of sheets of various kinds of sizes similarly to the above.
Corresponding thereto, the sheet discharge device is also to handle sheets of various kinds. A matching reference position of a sheet bundle is normally adjusted to one end side (hereinafter referred to as ┌reference side┘) perpendicular to the sheet discharge direction of a sheet discharge outlet to a stack tray. Accordingly, in the image forming apparatus, an image formed sheet is delivered at a position along the reference side to the sheet discharge device.
Therefore, the position of the staple means in the sheet discharge device is naturally arranged at a position on the reference side in the treating tray for carrying out the post-treatment such as matching of a sheet thereon, and the pressing means for pressing the other end of the sheet for adjusting one end of the sheet to be matched is to be arranged on the opposite side of the reference side in the treating tray. And, the matching reference of the sheet bundle is normally set to a fixed position at one place, and therefore, a matching reference portion for controlling the matching reference is provided on the reference side of the treating tray.
Incidentally, in the image forming apparatus and the sheet conveying mechanism in the sheet discharge device, the sheet is normally conveyed in the state that the sheet is nipped by the upper and lower paired rollers arranged at two places. It is desired that the paired rollers at two places are arranged at equal intervals from the center of the sheet. This is because of the fact that when the two paired rollers are at a position extremely different from the center, the conveying direction of the sheet becomes unstable, or the sheet moves obliquely to raise the dangerousness of jamming. However, the image forming apparatus and the sheet discharge device handle sheets of various sizes, and the sheets of various sizes are conveyed and discharged close to the reference side of one end of the device. Therefore, a sheet of the size smaller than that in a prescribed lateral width direction is nipped in the state of being offset greatly from the center of the position at which the paired rollers at two places, or nipping by one paired rollers on the side opposite the reference side becomes disengaged.
Therefore, for example, Japanese Patent Laid-Open No. 276691/1990 (a first prior art) discloses an image forming post-treatment device in which a pair of jogger fences (pressing means) carries out matching such that a sheet is moved close to the central portion of the device from both sides of the device.
Further, in the sheet post-treatment device described in Japanese Patent Laid-Open No. 109809/1998 (a second prior art), as shown in FIG. 11, a side fence 408 for determining a matching reference 408 and a jogger fence 402 corresponding to the pressing means of the present application are made to be independent by an individual driving portion, and to be movable according to the size of copy sheets, and a stapler 400 is moved integral with the side fence 408. Because of this, in the second prior art, the jogger fence 402 and the side fence 408 move along a guide shaft 417 secured perpendicular to the sheet discharge direction to a staple tray 401. The jogger fence 402 is moved through a timing belt 415 by a drive stepping motor 414, and the side fence 408 is moved by the drive stepping motor 411 and a timing belt 412. And, when a copy sheet is conveyed to a staple unit and a rear end of the copy sheet is received in a staple tray, the jogger fence 402 causes the end surface of the copy sheet to move in a direction of the side fence 408 to match it.
However, the post-treatment devices according to these prior arts are very complicated in mechanism, and even the device of the second prior art which is in the form of simplifying the first prior art, a mechanism for actuating the side fence 408 and the stapler 400 for controlling the matching reference and a mechanism for actuating the jogger fence 402 for moving a sheet to the side fence 408 separately therefrom are very complicated, making it difficult to achieve reduction in cost and miniaturization of the device size.
Further, since the side fence 408 and the stapler 400 move integrally, a stapling position applied to a sheet bundle is stabilized but a matching position moves as the stapler moves. The two operating mechanisms are complicated, and a long-period stability of the matching position is not obtained due to the looseness or slipping of the timing belts 411, 414 or the like, thus posing a problem in matching property.
Further, in a space where the stapler 400 moves, since no means for supporting a sheet is provided, sheets drop into the space, thus giving rise to a problem that accurate matching treatment fails to perform.
It is therefore an object of the present invention to provide a sheet discharge device and an image forming apparatus which solves the above-described problem in the sheet discharge device of the type which enables handling of sheets of various sizes by the provision of a plurality of matching reference positions, and which makes enabling a long-period stabilization of the matching performance.